Conventional ground fault circuit interrupting (GFCI) devices are currently being mass produced in circuit breaker and receptacle configurations for utilization in residential type circuits to protect personnel against the hazards of electrical shock due to ground faults. These GFCI devices include a differential current transformer having separate primary windings connected in the line and neutral sides of the circuit to be afforded ground fault protection. Any imbalance in the currents flowing in the line and neutral sides, as occasioned by current flowing through a line-to-ground fault and returning to the source through an extraneous ground circuit path, produces a signal in the differential current transformer secondary winding proportional to the current imbalance. Since for effective human shock protection, the GFCI device must respond to a 5 milliamp current imbalance, the transformer secondary signal must be processed by a module containing rather sophisticated and highly sensitive electronic circuitry pursuant to initiating a ground fault trip function leading to interruption of the circuit. Specifically, to effect a circuit interruption, the module acts to trigger an electronic switch, e.g., thyristor, thereby completing an energization circuit for a trip solenoid which acts to trip the GFCI device, causing its contacts, wired in the protected circuit, to spring open.
For the sake of convenience and efficiency of design, the active elements of the conventional GFCI device, i.e., trip solenoid and electronic module components, receive electrical power from the protected circuit downstream from the device circuit interrupting contacts. Since the typical residential-type circuit operates at 120 VAC, conventional GFCI modules are thus designed to operate at this voltage.
On occasion it would be desirable to afford personnel ground fault protection for special circuits operating at voltages other than 120 VAC. Unfortunately, since conventional GFCI devices are designed to operate properly only at 120 VAC, ground fault protection is not readily available for these special circuits.
It is accordingly a principal object of the present invention to provide a ground fault protector capable of affording personnel ground fault protection for special circuits operating at voltages other than the voltage conventional GFCI device electronic module circuitry is normally designed to accommodate.
A further object is to provide a ground protector of the above character, which is capable of utilizing conventional GFCI components.
Another object is to provide a ground fault circuit interrupting device of the above character which is efficient in design, inexpensive to manufacture and reliable in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.